[PATCH v2 3/7] firmware: dmi: Read additional information when decoding DMI table

Mario Limonciello (AMD)
2025-12-16T12:34:20Z

Type 40 entries (Additional information) are summarized in section
7.41 as part of the SMBIOS specification. Save these entries when
decoding the DMI tables.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
v2:
* Drop some unneeded variables (LKP robot)
* Allow any length strings, not just 5 and longer
---
drivers/firmware/dmi_scan.c | 38 +++++++++++++++++++++++++++++++++++++
include/linux/dmi.h | 7 +++++++
2 files changed, 45 insertions(+)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 80aded4c778bc..ec84fe3935c1e 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -393,6 +393,40 @@ static void __init dmi_save_dev_pciaddr(int instance, int segment, int bus,
list_add(&dev->dev.list, &dmi_devices);
}

+static void __init dmi_save_additional(const struct dmi_additional_info *info)
+{
+ const u8 *data;
+ int i;
+
+ if (!info || info->header.length < 5 + info->count * 5)
+ return;
+
+ data = info->entries;
+
+ for (i = 0; i < info->count; i++) {
+ u8 string_num = data[i * 5 + 4];
+ const char *string_ptr;
+ char *value;
+ int len;
+
+ string_ptr = dmi_string_nosave(&info->header, string_num);
+ if (!string_ptr || !*string_ptr)
+ continue;
+
+ len = strlen(string_ptr);
+ if (len == 0)
+ continue;
+
+ value = dmi_alloc(len + 1);
+ if (!value)
+ continue;
+
+ strscpy(value, string_ptr, len + 1);
+
+ dmi_save_one_device(DMI_DEV_TYPE_ADDITIONAL, value);
+ }
+}
+
static void __init dmi_save_extended_devices(const struct dmi_header *dm)
{
const char *name;
@@ -526,8 +560,12 @@ static void __init dmi_decode(const struct dmi_header *dm, void *dummy)
case DMI_ENTRY_IPMI_DEV:
dmi_save_ipmi_device(dm);
break;
+ case DMI_ENTRY_ADDITIONAL:
+ dmi_save_additional((const struct dmi_additional_info *)dm);
+ break;
case DMI_ENTRY_ONBOARD_DEV_EXT:
dmi_save_extended_devices(dm);
+ break;
}
}

diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index a809b5095c259..3fc3d334b321d 100644
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -24,6 +24,7 @@ enum dmi_device_type {
DMI_DEV_TYPE_OEM_STRING = -2,
DMI_DEV_TYPE_DEV_ONBOARD = -3,
DMI_DEV_TYPE_DEV_SLOT = -4,
+ DMI_DEV_TYPE_ADDITIONAL = -5,
};

enum dmi_entry_type {
@@ -87,6 +88,12 @@ struct dmi_device {
void *device_data; /* Type specific data */
};

+struct dmi_additional_info {
+ struct dmi_header header;
+ u8 count;
+ u8 entries[];
+} __packed;
+
#ifdef CONFIG_DMI

struct dmi_dev_onboard {
--
2.43.0